This short illustration is taken from Nate Jenkins' blog on RunningTimes.com. It goes over one of the major workouts I do: the 10x400 with 100m rest.
"I am not in anyway a fan of 10x400m with 1min recovery. Standing rest mean the workout improvements will not translate into race improvements. I do like using 10x400m at 10k pace with 100m run in 20 to 25 seconds for rest as a bit of a tempo workout to work on improving efficiency at 10k goal pace and to work on overall aerobic fitness- including threshold.Running workouts with too much rest and with standing rests is the one thing that is most responsible for holding back the performance of competitive runners. Particularly HS and college runners. A quick story to illustrate this point. When I was in HS I routinely did 8x400m in 65 or faster, including once averaging 60(which was huge given my 400m best was 58.8). The vast majority of say sub 10:30 HS males can and do this sort of session all the time. yet they don’t run 8:40 for two miles. The way i do my 8×400 now if I can run 65′s I may not run 8:40 but I’m going to be within a few seconds of it. It isn’t that I’m going easier in the workout, it is that I have set up the rest in a manner that helps the workout teach me to race well, rather then teach me to run intervals well.So the story a HS kid with a 4:36 mile PR goes on a college visit, he ends up doing a workout with some red shirting kids on the team that he meets, they are doing 8x400m and he is stunned when they tell him they are doing them in 70! This is much slower then the mid 60 pace he would normally run the workout in. On top of that the two red shirts have much faster PR’s then him. They tell him they are doing them with 200m jog rest. After the first 70- which feels like a walk to our HS hero- who’s two mile best at the time was over 10mins, they run the 200m rest in 45 seconds- this feels fine to our HS hero, but by the start of the third rep he has noticed that the 45 second 200 is leaving him very very tired, after the fourth 400- which he covers in 72 falling off the red shirts in the last 100 he is forced to stop the workout because he can’t keep up on the jog. Our HS hero is a smart fellow and he realizes that something about this workout must be touching on something he is missing in his training. So over the next 4 months he includes this session every week or so. by the end of those 4 months he runs just a shade over 4:10 in the mile. When planning the workout THE SINGLE MOST IMPORTANT factor is THE REST."
To read Nate's blog, go to www.runningtimes.com